The first recombinant plant-derived pharmaceutical protein (PDP) was human serum albumin, initially produced in 1990 in transgenic tobacco and potato plants. Fifteen years on, the first technical proteins produced in transgenic plants are on the market, and proof of concept has been established for the production of many therapeutic proteins, including antibodies, blood products, cytokines, growth factors, hormones, recombinant enzymes and human and veterinary vaccines. Furthermore, several PDP products for the treatment of human diseases are approaching commercialization, including recombinant gastric lipase for the treatment of cystic fibrosis, and antibodies for the prevention of dental caries and the treatment of non-Hodgkin's lymphoma. There are also several veterinary vaccines in the pipeline; Dow AgroSciences announced recently their intention to produce plant-based vaccines for the animal health industry.

Molecular farming (also known as molecular pharming or biopharming) is the use of genetically engineered crops to produce compounds with therapeutic value. These crops will become biological factories used to generate drugs and other difficult or expensive products. The term pharming can be used to describe plant derived pharmaceuticals, but it is more commonly used for products engineered in animals. The issue of genetically modified crops has been around for a number of years and continues to be a controversial subject.

Advantages
Plants do not carry pathogens that might be dangerous to human health. Additionally, on the level of pharmacologically active proteins, there are no proteins in plants that are similar to human proteins. On the other hand, plants are still sufficiently closely related to animals and humans that they are able to correctly process and configure both animal and human proteins. Their seeds and fruits also provide sterile packaging containers for the valuable therapeutics and guarantee a certain storage life.

Global demand for pharmaceuticals is at unprecedented levels, and current production capacity will soon be overwhelmed. Expanding the existing microbial systems, although feasible for some therapeutic products, is not a satisfactory option on several grounds. First, it would be very expensive for the pharmaceutical companies. Second, other proteins of interest are too complex to be made by microbial systems. These proteins are currently being produced in animal cell cultures, but the resulting product is often prohibitively expensive for many patients. Finally, although it is theoretically possible to synthesize protein molecules by machine, this works only for very small molecules, less than 30 amino acid residue in length. Virtually all proteins of therapeutic value are larger than this and require live cells to produce them. For these reasons, science has been exploring other options for producing proteins of therapeutic value.

Disadvantages
While molecular farming is one application of genetic engineering, there are concerns that are unique to it. In the case of genetically modified (GM) foods, concerns focus on the safety of the food for human consumption. In response, it has been argued that the genes that enhance a crop in some way, such as drought resistance or pesticide resistance, are not believed to affect the food itself. Other GM foods in development, such as fruits designed to ripen faster or grow larger, are believed not to affect humans any differently from non-GM varieties.

In contrast, molecular farming is not intended for crops destined for the food chain. It produces plants that contain physiologically active compounds that accumulate in the plant's tissues. Considerable attention is focused, therefore, on the restraint and caution necessary to protect both consumer health and environmental biodiversity.

Controversy
The fact that the plants are used to produce drugs is alarming activists. They worry that once production begins, the altered plants might find their way into the food supply or cross-pollinate with clean crops. Concern arose last year after GMO corn produced by StarLink accidentally ended up in commercial food products. No products produced by plant molecular farming were available in the emerging market, until the first ones were launch around 2006. Today Molecular Farming is considered "big business". According to the Canadian Food Inspection Agency, in a recent report, says that U.S. demand alone for biotech pharmaceuticals is expanding at 13 percent annually and to reach a market value of $28.6 billion in 2004. Molecular Farming is expected to be worth $100 billion globally by 2020.

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